why would I want this?

you can boot even with SATA-password set (for example to change/delete it with hdparm)

hotswap harddrive (didn't test, but should work)

it's cool.

okay, show me how!

preliminary actions

first you should update your existing BIOS. This is important as you cannot update your ECP version afterwards. Linux users can use the ISO files provided by Lenovo and do some nice trick described here

It is also advisable to save the output of dmidecode somewhere, as you need specific BIOS versions strings to get thinkpad_acpi to work.

next buy or build a SPI flasher and get a SOIC8 clip for mounting the chip correctly.

the ugly part

you have to dump the existing BIOS using flashrom and an external SPI flasher.
here's the pinout: